Single-step-model analysis of angle-resolved photoemission from Ni(110) and Cu(100)

Detailed computer calculations of angle-resolved photoemission are used to demonstrate that experimental data on Ni(110) and Cu(100) show effects that are found in the single-step model of photoemission, but not contained in the usual three-step model. In particular, the effect of inelastic scattering on the widths and shapes of direct-transition peaks is investigated directly and compared with simple line-shape formulas which are derived from the theory. Constant-initial-state spectra provide a particularly useful method for the determination of the inelastic scattering in the upper state. However, direct interpretation by a Lorentz-curve fit may overestimate the inelastic scattering slightly, since a somewhat smaller value is obtained by comparing the experiment with detailed calculations. Proper interpretation of the nickel data requires that the upper-state bands should be calculated including a damping due to inelastic scattering. Surface-matching effects appear to influence the shape of direct-transition peaks in copper.